The aim of the project is firstly to determine by single-crystal x-ray diffraction analysis the observed conformations and structures of psychoactive drugs, in particular neuroleptics and tricyclic anti-depressants; and secondly to determine by a study of the observed and possible conformations the conformation and pharmacodynamic groups required for the particular pharmacological activity. The determination of the conformation and pharmacodynamic groups relevant to interaction in a biological system is done by a study of rigid analogues and major use of a simple computer interactive graphics system which allows study of the possible conformations of molecules. BIBLIOGRAPHIC REFERENCES: Peter Pauling. The Significance of Conformation in Psychotherapeutic Drugs, E. Usdin and I.S. Forrest, Marcel Dekker, New York, 1976. N. Datta and P. Pauling. J. Chem. Soc. (Lon) Perk II (1977) in press.